This is Dudley Observatory’s Skywatch Line for Friday, June 10, through Sunday, June 12, written by Sam Salem.
The Sun rises at 5:17am and sets at 8:34pm on Friday. This is the earliest sunrise time of the year. Although the Northern Hemisphere’s longest day doesn’t occur until the summer solstice on June 20, earliest sunrise happens several days before and latest sunset happens several days after. The specific dates depend on latitude. For our area the earliest sunrise of this year occurs on June 8 through June 20. On those days the sun rises at 5:17am. The latest sunset of this year occurs starting from June 20 to July 2. On those days the sun sets at 8:38pm. In general, the farther north you live, earliest sunrise occurs closer to the summer solstice.
The First Quarter Moon occurs on at 4:10am on Sunday. The Moon rises around 11:11am on Friday. It sets at 12:42am on Saturday, 1:11am Sunday, and 1:40am on Monday.
Jupiter is visible in daylight, 4 degrees right of Moon on Saturday. This is not an easy observation as Jupiter is significantly dimmer than Venus and finding it takes more effort, and it depends on atmospheric conditions as well. The best time to look is near a “quadrature” when Jupiter is about 90 degrees away from the sun in the sky. The reason you want the planet at about 90 degrees from the sun is that the sky is slightly darker there due to polarization. To have the quarter Moon nearby helps to guide you to Jupiter.
Mars shrinks from 18.6 to 18.3 arcseconds in diameter. Neptune (magnitude 7.9) is in Aquarius up in the southeast just before dawn.
Asteroid 8 Flora (mag +9.4) is at opposition in Ophiuchus on Saturday. 8 Flora is the innermost large, bright, main-belt asteroid. It is the seventh brightest asteroid with a mean opposition magnitude of +8.7.
The Big Dipper is a circumpolar asterism, from our latitude, where all of its stars are visible regardless of the time of night or time of year. The Big and Little Dippers swing around the North Star Polaris. They go full circle around Polaris once a day, or once every 23 hours and 56 minutes. Imagine a star clock with the Big Dipper as the hand of a clock with Polaris in the dial’s center. The clock rotates counterclockwise as the Big Dipper moves in that direction. The hours are not stationary on this Star clock but they change every month. Due to the four-minute difference between the sidereal day and the solar day, the Big Dipper pointers will have rotated slightly further to the west at the same hour on each successive night, making a complete revolution over the course of the year. Therefore, each successive month, at the same time, the pointers will be approximately 1/12 of the way around the pole.
In a lecture on June 10, 1854, G.F. Bernhard Riemann proposed that space is curved. He suggested that all physical laws become simpler when expressed in higher dimensions. Albert Einstein in 1915 used Riemann’s work in his theory of General Relativity, incorporating time as the fourth dimension.